Is Mexico supported?


My prototypes largely cease functioning when they go into mexico. They are close to the border, so I think the few cases where they work they log into US towers. I am using an Arduino MKR GSM with the UBLOX SARA-U201.
Here the result of a unit right on the border, able to see both networks. It looks like I can manually log into the US networks fine, but not into TELCEL mexico.


+COPS: (2,“T-Mobile”,“T-Mobile”,“310260”,2),(1,“AT&T”,“AT&T”,“310410”,2),(2,“T-Mobile”,“T-Mobile”,“310260”,0),(1,“TELCEL”,“TELCEL”,“33420”,0),(0-6),(0-2)









Any suggestions would be appreciated.


It doesnt help solve your problem but it does look like TELCEL Mexico is supported in Hologram’s documentation (click on mexico): So it should work.

Some thoughts:

  1. It may be that the modem is not configured to connect to GSM networks. AT&T (“310410”) and T-Mobile (“310260”) have UTRAN (3G) available (its the “,2)” at the end of each item vs “,0)” ). So that may be why the modem connects to those networks. Even though a GSM T-mobile tower is available (2nd to last listing) I bet its connecting to the first one.
  2. Check the +URAT command and run AT+URAT? to see if GSM is selected as allowed (check the AT command manual). You may want to test by setting AT+URAT=0 to force the modem into 2G only mode and try to connect to the tower again.
  3. It may be that the modem can see the TELCEL tower but the signal strength / quality is too low to actually connect to it. Unfortunately I don’t think you can get signal strength of towers you aren’t connected to. You can lookup the +CGED command and read through the manual to see if the U201 can report this information.
  4. Lastly, not really a solution, but I have found other U-Blox modems somewhat finicky with being configured to smoothly jump between carriers and technologies. Even though the modem and simcard can give universal global coverage you may have to change some configurations in the modem to make it actually switch over and connect.

Best of luck, I hope some of this helps but you should be able to find a solution with your modem and Hologram simcard that works with 2G/3G TELCEL in Mexico.


Great tips @AndrewGifft

On top of that:
We have seen that sometimes it can take several minutes for a modem to try a new carrier when the current one disappears. How long do you usually wait for it to come up on the Mexico side?

One thing that would be interesting to try is doing a CFUN=0 and then CFUN=1 to reset the radio.


Thank you for that excellent reply!


I just wanted to thank you guys one more time and report that we have at least one (new) unit operating in Mexico now. It is not clear to me exactly why this one works now and the other ones did not. If we find out, I will report here.

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